Oligo stability in water at -20 C----pH of water

alex dobrovic adobrovi at medicine.adelaide.edu.au
Wed Aug 12 18:05:09 EST 1998


It doesn't matter what comes out of the MilliQ-the CO2 dissolves in the
water subsequently and there is nothing you can do about it- you have a
very weak solution of carbonic acid- but its buffering capacity is
negligible.

Using a stirrer at the same time as you are pHing will decrease the pH as
more CO2 tends to dissolve. Check this out!!

o>In article <19980812151539.19492.rocketmail at send102.yahoomail.com>,
>rjdudley at yahoo.com wrote:
>
>> The definition is true; however, Milli-Q is not "pure by definition"
>> water.  There are dissolved gasses (e.g., CO2, N2, O2).  CO2 is of
>> special importance, since it does play a role in buffering water (and
>> your blood) with the carbonate-bicarbonate buffering system.  The mere
>> act of retrieving water from the Milli-Q tap intorduces CO2.
>> Adidtionally, I don't think that Milli-Q (or other deionization
>> systems) scrub protons; they are more geared for nitrates, sulfates,
>> etc.
>
>Not true.
>Most Milli-Q systems have a .22um filter that is connected at point of
>dispencing, therefore, disolved gasses are virtually non-exsistant.  Also
>if your conductivity meter is working correctly and it reads >18MOhms then
>it is safe to say you have no ions.  Because if you did have ions then you
>would see a conductance of less than ~17 MOhms.
>Also most Milli-Q systems have a cartirage that is called a "polishing
>cartirage".  It is made up of activated carbon which will bind to
>uncharged molecules.  It works by a priciple called "adsorption".  With
>regard to carbon, all polar or species with lone pair electrons will
>bind.  The only way for them to be released is by heating the carbon up.
>The charged species that you mentioned will be removed by the initial
>cartridges which are made with Strong cation and Anion resin.
>If you allow your water to sit exposed to the atmossphere for any length
>of time then some C02 would disolve into solution and a buffer may form.
>
>Peter
>
>--
>"Don't you eat that yellow snow
>            watch out where the Huskies go"    FZ
>
>---------------------------------------------------------------------


Alexander Dobrovic, Ph.D.
Chief Medical Scientist
Department of Haematology-Oncology
The Queen Elizabeth Hospital
Woodville, SA 5011, Australia

Affiliate Senior Lecturer
Department of Medicine
University of Adelaide

Tel 61-8-8222 7676 (new as from April 1998)
Fax 61-8-8222 6046
adobrovi at medicine.adelaide.edu.au





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